We will continue our attempts to examine possible correlations between DNA metabolism and aging. In particular, we will examine the hypothesis that aspects of DNA metabolism may themselves produce lesions in cellular DNA, eventually evidenced as aging. We will examine in detail certain mechanisms we have observed in irradiated cells: DNA disassembly, DNA incision and ligation and removal of radiation-induced damage. These will be examined in cultured cell systems which may have relevance to aging hypotheses. In a more limited manner, certain repair processes will be measured in vivo in organisms of different age. BIBLIOGRAPHIC REFERENCES: Ehmann, U.K., J.R. Williams, W.A. Nagle, J.A. Brown, J.A. Belli, and J.T. Lett. "Perturbations in Cell Cycle Progression from Radioactive DNA Precursors." Nature 258:633-635, 1976. Williams, J.R. "The Role of DNA Repair in Cell Inactivation, Aging and Transformation: A Selective Review, A Speculative Model." In: Advances in Radiation Biology, Vol. 6., Academic Press, 1976.